Common end closures for beer and beverage containers have a central panel that has a frangible panel (sometimes called a “tear panel,” “opening panel,” or “pour panel”) defined by a score formed on the outer surface, the “public side,” of the end closure. Popular “ecology” can ends are designed to provide a way of opening the end by fracturing the scored metal of the panel, while not allowing separation of any parts of the end. For example, the most common such beverage container end has a tear panel that is retained to the end by a non-scored hinge region joining the tear panel to the reminder of the end, with a rivet to attach a leverage tab provided for opening the tear panel. This type of container end, typically called a “stay-on-tab” (“SOT”) end has a tear panel that is defined by an incomplete circular-shaped score, with the non-scored segment serving as the retaining fragment of metal at the hinge-line of the displacement of the tear panel.
The container is typically a drawn and ironed metal can, usually constructed from a thin plate of aluminum. End closures for such containers are also typically constructed from a cut-edge of thin plate of aluminum or steel, formed into a blank end, and manufactured into a finished end by a process often referred to as end conversion. These ends are formed in the process of first forming a cut-edge of thin metal, forming a blank end from the cut-edge, and converting the blank into an end closure which may be seamed onto a container. Although not presently a popular alternative, such containers and/or ends may be constructed of plastic material, with similar construction of non-detachable parts provided for openability.
These types of “stay-on-tab” ecology container ends have been used for many years, with a retained tab and a tear panel of various different shapes and sizes. Throughout the use of such ends, manufacturers have sought to save the expense of the metal by down-gauging the metal of the ends and the tabs. However, because ends are used for containers with pressurized contents and are sometimes subject to pasteurization, there are conditions causing great stresses to the components of the end during pasteurization, transit and during opening by a user. These conditions limit the available gauge reduction of the end metal, and make it difficult to alter design characteristics of the end, such as by reducing metal gauge or the thickness of the metal residual in the score defining the tear panel.
The pressurized contents of the container often cause risk for the end to buckle. The pressurized contents may also result in a condition in which the tab is forced upwardly. There is a maximum allowable distance that the tab can be displaced without the tab extending upwardly above the remainder of the container. This is called tab-over-chime. Tab-over-chime leads to ship abuse problems wherein the frangible panel prematurely fractures during distribution of filled beverage containers.
As manufacturers reduce the thickness of the metal used to make the ends, buckle and tab-over-chime become more and more of a problem. Therefore, a need for can end with improved ability to withstand buckle and tab-over-chime is needed.
Finished can ends, also referred to as reformed or converted can ends, are available in many sizes. The different sizes are generally identified as 200, 202, 206, and 209. The sizes are distinguished, in part, by their respective diameters. The 200 can end is the smallest, and the 209 is the largest.
A can end similar to one described in U.S. Pat. No. 7,819,275, which is hereby incorporated by reference as if fully set forth herein, has gained some commercial acceptance. A can shell illustrated in FIG. 13 of the '275 patent includes a circular center panel connected to a short, inclined, beveled panel wall. The inclined or beveled panel wall has straight inner and outer surfaces and extends at an acute angle, and connects through a vertical wall with an inclined inner wall of a countersink, which has a generally U-shaped cross sectional configuration. The countersink has an inclined outer wall and connects with a chuckwall having an inclined or curved upper wall portion and an inclined lower wall portion. An upper portion of the chuckwall connected to an inner wall portion of a crown having a curved outer wall.
The can end shell depicted in FIG. 13 of the '275 patent is generally formed from aluminum sheet having a thickness of about 0.0082 ins. When produced from thick aluminum stock such as this, the seamed can end reportedly exhibits suitable resistance to buckle. The configuration and relative shallow profile of the can shell also result in a seamed can end having an overall height of less than 0.240 ins, thus providing for a reduction of over 0.040 inch in the diameter of the circular blank which is used to form the shell. This reduction in diameter reportedly results in a significant reduction in the width of aluminum sheet used to produce the shells, thus a reduction in the weight and cost of aluminum to form can ends.
Co-pending and commonly assigned U.S. patent application Ser. No. 12/795,434 filed on Jun. 7, 2010, which is hereby incorporated by reference as if fully set forth herein, describes can ends or lids for two-piece metallic beverage cans produced from a reduced volume of metal, notably a blank of a reduced thickness. The can ends of the '434 application are generally 209 size can ends having a diameter of at least 60 mm, more likely about 70 mm or slightly less than 70 mm, about 65 mm when seamed to a can body.
It is desired to produce a can end which is produced from a metal blank having a thickness less than 0.0082 ins while maintaining an adequate buckle strength greater than 100 psi.
Generally, can end shells, i.e. those produced in a shell press, will exhibit dimensional variability, especially in the countersink area. It is believed that this is caused by grain orientation in the metal, primarily aluminum alloy, blanks used to produce the can end shells. Thus, from can end shell to can end shell, the dimensions will be fairly consistent. However, about the countersink of a single can end shell the dimensions will vary. Stated another way, inter-can end shell variability will generally be low while intra-can end shell variability can be relatively high.
A converted or finished can end produced from a can end shell exhibiting the inconsistency or variability described above can lead to difficulty in double seaming the converted can end to a can body because the seaming chuck inserted within the public side of the can end during seaming will not fit within the countersink exactly the same about the circumference of the can end. Therefore, the circumferential double seam may become undesirably variable or prone to failure.
The present invention is provided to solve the problems discussed above and other problems, and to provide advantages and aspects not provided by prior can ends or lids of this type. A full discussion of the features and advantages of the present invention is deferred to the following detailed description, which proceeds with reference to the accompanying drawings.